Sariel.pl

Big mobile crane, based on Liebherr LTM 1400. Features full suspension, 8 wheels drive, 10 wheels steering, 3-section telescopic boom with a 2-block situation indicator, star system outriggers and V8 piston engine. Built entirely in Technicfig scale.

Datasheet:

Completion date: 29/12/2007
Power: electric (Power Functions) / pneumatic (fed from internal electric compressor nad internal manual pump)
Dimensions: length 125 studs / width 22 studs / height 33 studs
Weight: approx. 5 kg
Suspension: full pendular without shock absorbers
Motors: 2 x PF XL, 2 x PF Medium, 1 x RC
Pneumatics: two circuits with internal electric compressor, and additional manual pump with an airtank

An ultimate result of a fascination by the mobile cranes. I have spent a lot of time since my previous crane was built, planning how to make the next one better. In the meantime I’ve finally bought the 8421 set, which has greatly influenced the project.

The boom was the first thing I’ve built. It consists of 3 sections, with the same extension mechanism by Jennifer Clark as in the last crane, using hybrid rack & pinion plus pulleys system. The boom weights approx. 1.2 kg and can be extended from 112 to 290 studs (approx. 2.3 meter). It is fully covered, with all the mechanics and ropes included inside. The third section of the boom includes the LED brick from Exo-Force sets, which turns on when the third and second section are squeezed together. This situation, when the boom is being retracted too far back, is called a 2-block situation, and the LED brick is intended to indicate when it’s about to happen. As the linear actuators were still unavailable at the time the crane was built, I have designed my own mechanic cylinder, which was huge and looked unrealistic, but proved able to lift and support the boom.

The carrier was the second thing to be built, and the most complex one. Most of the space inside is taken by the suspension, drivetrain and steering systems. There are basically three systems of axles: axles 1 & 2 are steered and driven, axles 3 & 4 are only driven, and axles 5, 6 & 7 are only steered. All axles have pendular suspension, most of them with transverse modules without shock absorbers. The crane is kept stable by axles 3 & 4 which use longitudinal modules. The steered axles obviously feature various steering ratio. The carrier is kept together by a complex frame, strong enough to let the crane be carried by a hand. The frame required a lot of planning, as it had to be as strong and compact as possible, as well as to be placed in the upper part of the carrier, as the space below was needed for suspension. Finally, the frame consists of a number of smaller modules joined using Technic Pins Long with Stop Bush, simply to make the assembly easier – it would be quite a bother to be forced to move the entire 1-meter long structure every time the access to its other side was needed. Front part of the carrier includes a PF battery box, a V8 piston engine, and a Technicfig-scale cab with a functional steering wheel. There is also simple amortized bed to support lowered boom – a solution present in the real Liebherr crane. In the middle of the carrier, there are 4 star-system outriggers that are deployed and lowered by two pneumatic circuits.

The superstructure is connected to the carrier by a regular Technic turntable of the newer type. It turned out to be a bad idea, as the turntable was unable to withstand the tensions generated by the elevated and extracted boom. The lack of space in the carrier forced me to locate an electric compressor in the superstructure. It was driven by an RC motor powered from the old-type battery box attached at the back of the superstructure, as a counterbalance. Since the compressor had low efficience, I have added a manual pump with an airtank attached to the pneumatic system, to be used in need of a high pressure. It was in fact unnecessary, as the pneumatics powered only the outriggers, which don’t require much pressure. There is also a PF XL motor that drives the winch inside the superstructure. My intent of using it to extend the boom failed due to the transmission between the motor and the boom being too weak. The boom was eventually extended manually by a crank. There is also a V4 piston engine in the superstructure, as the real Liebherr crane has a separate superstructure engine.

The crane has been a very aspiring project, perhaps too aspiring in face of the lack of linear actuators. Many solutions that worked well in smaller models were rendered useless here by the sheer size and weight of the vehicle. It has, however, been a precious experience, that taught me a lot about the limitations implied by the huge size of a model. One year later, it still remains the biggest thing I’ve ever built.

Photos:

Video: